In a principal aspect, the present invention relates to a combination ground and power source device for use in a cigarette lighter receptacle of a vehicle. The device provides both a ground connection as well as a 12-volt power connection depending upon the terminals of the device which are connected in a circuit. Further, there is an indicator light which identifies whether the system contacts are powered or activated.
Automotive mechanics often need an effective ground to check electrical circuits in a vehicle. Additionally, a power connection is often required to test a circuit or a device. The cigarette lighter receptacle (now often termed the accessory receptacle) in a vehicle has been used to provide power for various purposes, including mobile phones, radar detectors, radios, and circuit testers. Typically, a special plug is provided to fit into the receptacle with leads that connect to the phone, etc. U.S. Pat. No. 4,540,940 discloses an example of a device capable of deriving power from a receptacle in a vehicle.
The use of a device of this nature to provide a ground, as well as a power source, has also been suggested. Applicants' assignee has, for example, as early as 1988, received suggestions of this general nature. There remains, however, the need for a practical, useful, efficient and rugged device of this type. In view of this background, the present device, having a positive and a negative or ground contact for circuit and device testing, was developed.